Multipoint fixation implants

ABSTRACT

Bone anchor assemblies are disclosed herein that can provide for improved fixation as compared with traditional bone anchor assemblies. An exemplary assembly can include a bracket or wing that extends down from the receiver member and accommodates one or more auxiliary bone anchors that augment the fixation of the assembly&#39;s primary bone anchor. Another exemplary assembly can include a plate that is seated between the receiver member and the rod and accommodates one or more auxiliary bone anchors that augment the fixation of the assembly&#39;s primary bone anchor. Another exemplary assembly can include a hook that extends out from the receiver member to hook onto an anatomical structure or another implant to augment the fixation of the assembly&#39;s primary bone anchor. Surgical methods using the bone anchor assemblies described herein are also disclosed.

FIELD

Orthopedic implants and related methods are disclosed herein. Forexample, bone anchor assemblies with multiple bone engagement points aredisclosed.

BACKGROUND

Bone anchor assemblies can be used in orthopedic surgery to fix boneduring healing, fusion, or other processes. In spinal surgery, forexample, bone anchor assemblies can be used to secure a spinal fixationelement to one or more vertebrae to rigidly or dynamically stabilize thespine. Bone anchor assemblies can also be used as an engagement pointfor manipulating bone (e.g., distracting, compressing, or rotating onevertebra with respect to another vertebra, reducing fractures in a longbone, and so forth).

The integrity with which the bone anchor assembly engages the bone canaffect the transfer of corrective biomechanical forces. While a greatamount of care is exercised when placing bone anchor assemblies, it iscommon that a bone anchor assembly will be inserted in a compromisedstate. For example, the bone opening in which the assembly is disposedcan be stripped (e.g., by driving the bone anchor assembly past itsoptimum holding position), the bone anchor assembly can be placedincorrectly (e.g., using an incorrect instrument maneuver such as anover-sized pilot hole), the bone anchor assembly can be placed outsideof its intended trajectory (e.g., within a facet capsule or breachedthrough a pedicle wall), or the bone anchor assembly can be insertedinto compromised bone (e.g., bone that is fractured, osteoporotic,diseased, or otherwise lacking in structural integrity).

When the bone anchor assembly is in a compromised state, there can besub-optimal purchase between the bone anchor assembly and the bone. Thebone anchor assembly may feel unsecure to the surgeon, and it ispossible that the bone anchor assembly could back out or become loosenedover time. There are limited options for the surgeon when faced withthese types of situations. In spinal surgery, for example, the surgeoncan remove the bone anchor assembly and skip the vertebral level, thoughthis can undesirably require expanding the surgical site to additionalvertebral levels. The surgeon can remove and re-insert with a largeranchor, though this may not be an option when space for anchoring in thebone is limited. The surgeon can leave the compromised bone anchorassembly in place, which may be the safest alternative if the boneanchor assembly is in a safe location and attachment to the plate, rod,or other implant construct is definitive, as the additional compromisedfixation may be better than removal.

Even when a bone anchor assembly is placed in a non-compromised state,the geometry of traditional bone anchor assemblies can limit theflexibility with which the bone attachment point can be located withrespect to a plate, rod, or other implant construct coupled to the boneanchor assembly.

There is a continual need for improved bone anchor assemblies andrelated methods.

SUMMARY

Bone anchor assemblies are disclosed herein that can provide forimproved fixation as compared with traditional bone anchor assemblies.An exemplary assembly can include a bracket or wing that extends downfrom the receiver member and accommodates one or more auxiliary boneanchors that augment the fixation of the assembly's primary bone anchor.Another exemplary assembly can include a plate that is seated betweenthe receiver member and the rod and accommodates one or more auxiliarybone anchors that augment the fixation of the assembly's primary boneanchor. Another exemplary assembly can include a hook that extends outfrom the receiver member to hook onto an anatomical structure or anotherimplant to augment the fixation of the assembly's primary bone anchor.Surgical methods using the bone anchor assemblies described herein arealso disclosed.

In some embodiments, a bone anchor assembly includes a bone anchor; areceiver member coupled to a proximal end of the bone anchor anddefining a recess configured to receive a rod; a closure mechanismthreadably mated to the receiver member; a wing having a proximalportion disposed proximal to the receiver member, a distal portion thatdefines a bone anchor opening, and a spanning portion that connects theproximal and distal portions; and a nut configured to threadably engagethe closure mechanism to secure the proximal portion of the wing to theproximal end of the receiver member.

The closure mechanism can be or can include a threaded post. The wingcan include an opening through which at least a portion of the threadedpost is disposed. The wing can be rotatable about the closure mechanism.A distal-facing surface of the proximal portion of the wing can bearagainst a proximal terminal end of the receiver member. A lateralsurface of the distal portion of the wing can form a negative of asidewall of the receiver member. A lateral surface of the spanningportion of the wing can form a negative of a sidewall of the receivermember. A lateral surface of the spanning portion of the wing caninclude a protrusion that engages a corresponding recess formed in thereceiver member. The spanning portion can hug the sidewall of thereceiver member. The receiver member can be polyaxially movable relativeto the bone anchor. The assembly can include an auxiliary bone anchordisposed in the bone anchor opening of the distal portion of the wing.The proximal-most extent of the auxiliary bone anchor can be distal to arod when the rod is disposed in the recess of the receiver member. Theproximal-most extent of the auxiliary bone anchor can be distal to thedistal-most extent of the receiver member. The spanning portion can havean adjustable height. The spanning portion can include first and secondlegs movable toward one another to increase the height of the spanningportion and movable away from one another to decrease the height of thespanning portion. The spanning portion can be deformable to allow thedistal portion of the wing to be angled to match an abutting bonesurface.

In some embodiments, a method of securing a bone anchor assembly to boneincludes driving a bone anchor into bone, the bone anchor having areceiver member coupled to a proximal end thereof; positioning a rod inthe receiver member; attaching a closure mechanism to the receivermember to retain the rod in the receiver member; coupling a proximalportion of a wing to at least one of the closure mechanism and aproximal surface of the receiver member; and inserting an auxiliary boneanchor through a bone anchor opening formed in a distal portion of thewing and driving the auxiliary bone anchor into the bone.

Coupling the proximal portion of the wing can include inserting at leasta portion of the closure mechanism through an opening formed in theproximal portion of the wing. The method can include rotating the wingrelative to receiver member to position the bone anchor opening of thewing with respect to a target location on the bone. The method caninclude deforming the wing to position the bone anchor opening of thewing with respect to a target location on the bone. The method caninclude adjusting a height of the wing such that the wing spans from theproximal-most extent of the receiver member to the bone. The bone anchorand the auxiliary bone anchor can be driven into a single vertebra.

In some embodiments, a bone anchor assembly includes a bone anchor; areceiver member coupled to a proximal end of the bone anchor anddefining a recess configured to receive a rod; a closure mechanismthreadably mated to the receiver member; a plate having a primaryopening through which first and second arms of the receiver memberextend, a bone anchor opening, and a saddle portion that extends acrossat least a portion of the primary opening such that the saddle portionis disposed in the recess of the receiver member; and an auxiliary boneanchor disposed through the bone anchor opening of the plate.

The assembly can include a rod disposed between the saddle portion ofthe plate and the closure mechanism. The saddle portion can be movablycoupled to the plate. A distal facing surface of the saddle portion canform a section of a cylinder. The primary opening in the plate can bedefined by a first sidewall. The bone anchor opening of the plate can bedefined by a second sidewall. A height of the first sidewall can bereduced where the first sidewall meets the second sidewall. The assemblycan include a cap configured to engage the first and second arms of thereceiver member. The cap can define a central opening disposed proximalto a proximal-most extent of the receiver member. The central openingcan receive at least a portion of the closure mechanism therethrough.The proximal-most extent of the auxiliary bone anchor can be distal to arod when the rod is disposed in the recess of the receiver member. Theproximal-most extent of the auxiliary bone anchor can be distal to thedistal-most extent of the receiver member.

In some embodiments, a method of securing a bone anchor assembly to boneincludes driving a bone anchor into bone, the bone anchor having areceiver member coupled to a proximal end thereof; inserting first andsecond arms of the receiver member through a primary opening of a platesuch that a saddle portion of the plate is disposed in a rod-receivingrecess of the receiver member; positioning a rod on a proximal-facingsurface of the saddle portion such that the rod is disposed in therod-receiving recess of the receiver member; attaching a closuremechanism to the receiver member to retain the rod in the receivermember; and inserting an auxiliary bone anchor through a bone anchoropening formed in the plate and driving the auxiliary bone anchor intothe bone.

The method can include bending the plate to position the bone anchoropening against the bone. The method can include bending the saddleportion of the plate to position the bone anchor opening against thebone. The bone anchor and the auxiliary bone anchor can be driven into asingle vertebra.

In some embodiments, a bone anchor assembly includes a bone anchor; areceiver member coupled to a proximal end of the bone anchor anddefining a recess configured to receive a rod; a closure mechanismthreadably mated to the receiver member; a plate having a primaryopening through which at least a portion of the receiver member extends,a bone anchor opening, and a distal-facing portion that extends across aproximal-facing portion of the receiver member; and an auxiliary boneanchor disposed through the bone anchor opening of the plate.

In some embodiments, a bone anchor assembly includes a bone anchor; areceiver member coupled to a proximal end of the bone anchor anddefining a recess configured to receive a rod; a closure mechanismthreadably mated to the receiver member; and a hook having a bodyportion coupled to the receiver member and a curved extension projectingfrom the body portion.

The extension can be substantially U-shaped. The extension can define aninside curved surface and an outside curved surface. The inside curvedsurface can form a substantial negative of a lamina. The body portioncan have a lateral sidewall that abuts a sidewall of the receivermember. The hook can be coupled to the receiver member by a collar. Thecollar can define a first opening in which the receiver member isdisposed and a second opening through which a locking screw is disposed.The locking screw can threadably engage the body portion of the hook.The first opening can include an engagement feature that engages acorresponding engagement feature formed in or on an exterior of thereceiver member. The second opening can have a tapered shape to pull thereceiver member towards the body portion as the locking screw istightened. The collar can be disposed proximal to a rod when the rod isdisposed in the receiver member. The collar can extend around an outerperiphery of the receiver member. The hook can be configured to pivotwith the receiver member relative to the bone anchor. The hook can becoupled to the receiver member by a nut. The nut can be threaded ontothe closure mechanism to compress a proximal portion of the hook againsta proximal end of the receiver member.

In some embodiments, a method of securing a bone anchor assembly to boneincludes driving a bone anchor into bone, the bone anchor having areceiver member coupled to a proximal end thereof; positioning a rodwithin a rod-receiving recess of the receiver member; attaching a hookto the receiver member and hooking an extension of the hook onto atleast one of an anatomical structure and an implant; and attaching aclosure mechanism to the receiver member to retain the rod in thereceiver member.

The bone anchor can be driven into a first vertebra and the extension ofthe hook can be hooked onto a lamina of the first vertebra. The hook canbe attached to the receiver member after the bone anchor is driven intothe bone. The closure mechanism can be attached to the receiver memberafter the hook is attached to the receiver member. The hook can beattached to the receiver member after the rod is seated in the receivermember.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an exploded perspective view of a prior art bone anchorassembly;

FIG. 1B is a sectional view of the bone anchor assembly of FIG. 1A;

FIG. 1C is a perspective view of the bone anchor assembly of FIG. 1Ashown with extension tabs;

FIG. 2A is a perspective view of a bone anchor assembly and a spinalrod;

FIG. 2B is a perspective exploded view of the bone anchor assembly andspinal rod of FIG. 2A;

FIG. 2C is a perspective view of the bone anchor assembly and spinal rodof FIG. 2A;

FIG. 2D is a top view of the bone anchor assembly and spinal rod of FIG.2A;

FIG. 2E is a perspective view of a wing of the bone anchor assembly ofFIG. 2A;

FIG. 2F is another perspective view of a wing of the bone anchorassembly of FIG. 2A;

FIG. 2G is another perspective view of a wing of the bone anchorassembly of FIG. 2A;

FIG. 2H is another perspective view of a wing of the bone anchorassembly of FIG. 2A;

FIG. 2I is a perspective view of the bone anchor assembly and spinal rodof FIG. 2A, shown with an adjustable-height wing;

FIG. 2J is a perspective view of a wing of the bone anchor assembly ofFIG. 2I;

FIG. 2K is another perspective view of a wing of the bone anchorassembly of FIG. 2I;

FIG. 2L is another perspective view of a wing of the bone anchorassembly of FIG. 2I;

FIG. 2M is another perspective view of a wing of the bone anchorassembly of FIG. 2I;

FIG. 3A is a perspective view of a bone anchor assembly and a spinalrod;

FIG. 3B is a perspective exploded view of the bone anchor assembly andspinal rod of FIG. 3A;

FIG. 3C is a perspective view of a plate of the bone anchor assembly ofFIG. 3A;

FIG. 3D is another perspective view of a plate of the bone anchorassembly of FIG. 3A;

FIG. 3E is another perspective view of a plate of the bone anchorassembly of FIG. 3A;

FIG. 3F is another perspective view of a plate of the bone anchorassembly of FIG. 3A;

FIG. 3G is a perspective view of a receiver member and plate of the boneanchor assembly of FIG. 3A;

FIG. 3H is a perspective view of the bone anchor assembly and spinal rodof FIG. 3A, shown with a cap;

FIG. 3I is a perspective view of a human spine with the bone anchorassembly and spinal rod of FIG. 3A coupled thereto;

FIG. 4A is a perspective view of a bone anchor assembly and a spinal rodcoupled to a human spine;

FIG. 4B is a perspective exploded view of the bone anchor assembly andspinal rod of FIG. 4A;

FIG. 4C is a perspective view of a hook of the bone anchor assembly ofFIG. 4A;

FIG. 4D is a perspective view of the bone anchor assembly of FIG. 4Abeing assembled in situ; and

FIG. 4E is a perspective view of the bone anchor assembly of FIG. 4Ashown with an alternate hook attachment.

DETAILED DESCRIPTION

Bone anchor assemblies are disclosed herein that can provide forimproved fixation as compared with traditional bone anchor assemblies.An exemplary assembly can include a bracket or wing that extends downfrom the receiver member and accommodates one or more auxiliary boneanchors that augment the fixation of the assembly's primary bone anchor.Another exemplary assembly can include a plate that is seated betweenthe receiver member and the rod and accommodates one or more auxiliarybone anchors that augment the fixation of the assembly's primary boneanchor. Another exemplary assembly can include a hook that extends outfrom the receiver member to hook onto an anatomical structure or anotherimplant to augment the fixation of the assembly's primary bone anchor.Surgical methods using the bone anchor assemblies described herein arealso disclosed.

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the systems and methods disclosed herein. One ormore examples of these embodiments are illustrated in the accompanyingdrawings. Those skilled in the art will understand that the systems andmethods specifically described herein and illustrated in theaccompanying drawings are non-limiting exemplary embodiments. Thefeatures illustrated or described in connection with one exemplaryembodiment may be combined with the features of other embodiments.

Prior Art Bone Anchor Assembly

FIGS. 1A-1C illustrate a prior art bone anchor assembly 100 with variousfeatures that can be included in the bone anchor assemblies 200, 300,400 described below. It will be appreciated that the illustrated boneanchor assembly 100 is exemplary and that the bone anchor assemblies200, 300, 400 can include additional or alternative features.

The illustrated bone anchor assembly 100 includes a bone anchor 102, areceiver member 104 for receiving a spinal fixation element, such as aspinal rod 106, to be coupled to the bone anchor 102, and a closuremechanism 108 to capture a spinal fixation element within the receivermember and fix the spinal fixation element with respect to the receivermember. The bone anchor 102 includes a proximal head 110 and a distalshaft 112 configured to engage bone. The receiver member 104 has aproximal end having a pair of spaced apart arms 114A, 114B defining arecess 116 therebetween and a distal end having a distal end surfacedefining an opening through which at least a portion of the bone anchor102 extends. The closure mechanism 108 can be positionable between andcan engage the arms 114A, 114B to capture a spinal fixation element,e.g., a spinal rod 106, within the receiver member 104 and fix thespinal fixation element with respect to the receiver member.

The proximal head 110 of the bone anchor 102 is generally in the shapeof a truncated sphere having a planar proximal surface and anapproximately spherically-shaped distal surface. The illustrated boneanchor assembly 100 is a polyaxial bone screw designed for posteriorimplantation in the pedicle or lateral mass of a vertebra. The proximalhead 110 of the bone anchor 102 engages the distal end of the receivermember 104 in a ball and socket like arrangement in which the proximalhead and the distal shaft 112 can pivot relative to the receiver member.The distal surface of the proximal head 110 of the bone anchor 102 and amating surface within the distal end of the receiver member 104 can haveany shape that facilitates this arrangement, including, for example,spherical (as illustrated), toroidal, conical, frustoconical, and anycombinations of these shapes.

The distal shaft 112 of the bone anchor 102 can be configured to engagebone and, in the illustrated embodiment, includes an external boneengaging thread. The thread form for the distal shaft 112, including thenumber of threads, the pitch, the major and minor diameters, and thethread shape, can be selected to facilitate connection with bone.Exemplary thread forms are disclosed in U.S. Patent ApplicationPublication No. 2011/0288599, filed on May 18, 2011, and in U.S. PatentApplication Publication No. 2013/0053901, filed on Aug. 22, 2012, bothof which are hereby incorporated by reference herein. The distal shaft112 can also include other structures for engaging bone, including ahook. The distal shaft 112 of the bone anchor 102 can be cannulated,having a central passage or cannula extending the length of the boneanchor to facilitate delivery of the bone anchor over a guidewire in,for example, minimally-invasive procedures. Other components of the boneanchor assembly 100, including, for example, the closure mechanism 108,the receiver member 104, and the compression member or cap 118(discussed below) can be cannulated or otherwise have an opening topermit delivery over a guidewire. The distal shaft 112 can also includeone or more sidewall openings or fenestrations that communicate with thecannula to permit bone in-growth or to permit the dispensing of bonecement or other materials through the bone anchor 102. The sidewallopenings can extend radially from the cannula through the sidewall ofthe distal shaft 112. Exemplary systems for delivering bone cement tothe bone anchor assembly 100 and alternative bone anchor configurationsfor facilitating cement delivery are described in U.S. PatentApplication Publication No. 2010/0114174, filed on Oct. 29, 2009, whichis hereby incorporated by reference herein. The distal shaft 112 of thebone anchor 102 can also be coated with materials to permit bone growth,such as, for example, hydroxyapatite, and the bone anchor assembly 100can be coated partially or entirely with anti-infective materials, suchas, for example, tryclosan.

The proximal end of the receiver member 104 includes a pair of spacedapart arms 114A, 114B defining a U-shaped recess 116 therebetween forreceiving a spinal fixation element, e.g., a spinal rod 106. Each of thearms 114A, 114B can extend from the distal end of the receiver member104 to a free end. The outer surfaces of each of the arms 114A, 114B caninclude a feature, such as a recess, dimple, notch, projection, or thelike, to facilitate connection of the receiver member 104 toinstruments. For example, the outer surface of each arm 114A, 114B caninclude an arcuate groove at the respective free end of the arms. Suchgrooves are described in more detail in U.S. Pat. No. 7,179,261, issuedon Feb. 20, 2007, which is hereby incorporated by reference herein.

The distal end of the receiver member 104 includes a distal end surfacewhich is generally annular in shape defining a circular opening throughwhich at least a portion of the bone anchor 102 extends. For example,the distal shaft 112 of the bone anchor 102 can extend through theopening.

The bone anchor 102 can be selectively fixed relative to the receivermember 104. Prior to fixation, the bone anchor 102 is movable relativeto the receiver member 104 within a cone of angulation generally definedby the geometry of the distal end of the receiver member and theproximal head 110 of the bone anchor 102. The bone anchor assembly 100can be a favored angle screw, for example as disclosed in U.S. Pat. No.6,974,460, issued on Dec. 13, 2005, and in U.S. Pat. No. 6,736,820,issued on May 18, 2004, both of which are hereby incorporated byreference herein. Alternatively, the bone anchor assembly 100 can be aconventional (non-biased) polyaxial screw in which the bone anchor 102pivots in the same amount in every direction.

The spinal fixation element, e.g., the spinal rod 106, can eitherdirectly contact the proximal head 110 of the bone anchor 102 or cancontact an intermediate element, e.g., a compression member 118. Thecompression member 118 can be positioned within the receiver member 104and interposed between the spinal rod 106 and the proximal head 110 ofthe bone anchor 102 to compress the distal outer surface of the proximalhead into direct, fixed engagement with the distal inner surface of thereceiver member 104. The compression member 118 can include a pair ofspaced apart arms 120A and 120B defining a U-shaped seat 122 forreceiving the spinal rod 106 and a distal surface for engaging theproximal head 110 of the bone anchor 102.

The proximal end of the receiver member 104 can be configured to receivea closure mechanism 108 positionable between and engaging the arms 114A,114B of the receiver member. The closure mechanism 108 can be configuredto capture a spinal fixation element, e.g., a spinal rod 106, within thereceiver member 104, to fix the spinal rod relative to the receivermember, and to fix the bone anchor 102 relative to the receiver member.The closure mechanism 108 can be a single set screw having an outerthread for engaging an inner thread provided on the arms 114A, 114B ofthe receiver member 104. In the illustrated embodiment, however, theclosure mechanism 108 includes an outer set screw 124 operable to act onthe compression member 118 and an inner set screw 126 operable to act onthe rod 106. The receiver member 104 can include, can be formedintegrally with, or can be coupled to one or more extension tabs 128(shown in FIG. 1C) that extend proximally from the receiver member 104to functionally extend the length of the arms 114A, 114B. The extensiontabs 128 can facilitate installation and assembly of a fixation orstabilization construct and can be removed prior to completing asurgical procedure.

The bone anchor assembly 100 can be used with a spinal fixation elementsuch as rigid spinal rod 106. Alternatively, the spinal fixation elementcan be a dynamic stabilization member that allows controlled mobilitybetween the instrumented vertebrae.

In use, the bone anchor assembly 100 can be assembled such that thedistal shaft 112 extends through the opening in the distal end of thereceiver member 104 and the proximal head 110 of the bone anchor 102 isreceived in the distal end of the receiver member 104. A driverinstrument can be fitted with the bone anchor 102 to drive the boneanchor into bone. The compression member 118 can be positioned withinthe receiver member 104 such that the arms 120A, 120B of the compressionmember are aligned with the arms 114A, 114B of the receiver member 104and the lower surface of the compression member 118 is in contact withthe proximal head 110 of the bone anchor 102. A spinal fixation element,e.g., the spinal rod 106, can be located in the recess 116 of thereceiver member 104. The closure mechanism 108 can be engaged with theinner thread provided on the arms 114A, 114B of the receiver member 104.A torsional force can be applied to the outer set screw 124 to move itwithin the recess 116 so as to force the compression member 118 onto theproximal head 110 of the bone anchor 102, thereby locking the angularposition of the bone anchor 102 relative to the receiver member 104. Atorsional force can be applied to the inner set screw 126 to force thespinal rod 106 into engagement with the compression member 118 andthereby fix the spinal rod 106 relative to the receiver member 104.

The bone anchor assemblies 200, 300, 400 described below can beconfigured to operate in conjunction with, or can include any of thefeatures of, bone anchor assemblies of the type described above or othertypes known in the art. Exemplary bone anchor assemblies includemonoaxial screws, polyaxial screws, uniplanar screws, favored-anglescrews, and/or any of a variety of other bone anchor types known in theart. Further information on favored-angle screws can be found in U.S.Patent Application Publication No. 2013/0096618, filed on Oct. 9, 2012,which is hereby incorporated by reference herein.

Multipoint Fixation Implants

FIGS. 2A-2M illustrate an exemplary embodiment of a bone anchor assembly200, shown with a spinal rod 206. As noted above, a bone anchor cansometimes be inserted in a compromised state. This can be undesirable,especially in the cervical region of the spine where there is limitedbone area in which to install additional bone anchors. The illustratedbone anchor assembly 200 can allow for supplemental fixation of aprimary bone anchor in a compact footprint, without necessarilyrequiring removal or re-insertion of the primary bone anchor. As shown,the bone anchor assembly 200 can include a bone anchor 202, a receivermember 204, a closure mechanism 208, a bracket or wing 230, a nut 232,and one or more auxiliary bone anchors 234. In use, the wing 230 can besecured to the receiver member 204, e.g., using the closure mechanism208 and nut 232, thereby providing the ability to augment fixation ofthe bone anchor 202 with the one or more auxiliary bone anchors 234.

Except as described below or as will be readily appreciated by onehaving ordinary skill in the art, the bone anchor 202 and receivermember 204 are substantially similar to the bone anchor 102 and receivermember 104 described above. A detailed description of the structure andfunction thereof is thus omitted here for the sake of brevity. The boneanchor assembly 200 can include any one or more of the features of thebone anchor assembly 100 described above.

The closure mechanism 208 can be selectively secured to the receivermember 204 to capture a spinal fixation element, e.g., a spinal rod 206,within the receiver member. Tightening or locking the closure mechanism208 can be effective to fix the spinal rod 206 relative to the receivermember 204, and to fix an angular position of the bone anchor 202relative to the receiver member 204. The illustrated closure mechanism208 is in the form of a threaded post with an enlarged-diameter distalportion 208 d and a reduced-diameter proximal portion 208 p. In otherembodiments, the proximal and distal portions 208 p, 208 d can have thesame diameter, or the proximal portion can have a diameter greater thanthat of the distal portion. The distal portion 208 d of the closuremechanism 208 can be threaded into the receiver member 204 to engage aspinal rod 206 disposed in the receiver member. The proximal portion 208p of the closure mechanism 208 can protrude above the receiver member204, e.g., above a proximal-facing terminal end surface of the receivermember, and through an opening 236 formed in the wing 230, as describedfurther below.

In the illustrated embodiment, the closure mechanism 208 bears directlyagainst the spinal rod 206, which in turn bears directly against thehead of the bone anchor 202. It will be appreciated, however, that oneor more intermediate elements can also be included in the bone anchorassembly 200. For example, the bone anchor assembly 200 can include acompression member of the type described above disposed between thespinal rod 206 and the head of the bone anchor 202. The closuremechanism 208 can be a single set screw as shown, or can include anouter set screw operable to act on a compression member and an inner setscrew operable to act on the rod 206. The closure mechanism 208 caninclude a driving interface (e.g., torx, flathead, Phillips head,square, or otherwise) to facilitate rotational advancement or retractionof the closure mechanism relative to the receiver member 204 using adriver instrument.

The nut 232 can include a central opening 238 sized to receive at leasta portion of the proximal end 208 p of the closure mechanism 208therethrough. The central opening 238 can include an internal threadthat corresponds to the external thread of the closure mechanism 208,such that the nut 232 can be threaded onto the closure mechanism andtightened to secure the wing 230 to the closure mechanism and thereceiver member 204 in which the closure mechanism is disposed. Theouter surface of the nut 232 can be faceted or otherwise configured tofacilitate application of torque to the nut. In some embodiments, thenut 232 can have a hexagonal or square cross-section.

As shown in FIGS. 2E-2H, the bracket or wing 230 can include a proximalportion 230 p that can contact the receiver member 204, a distal portion230 d that can contact a bone surface or be disposed in close proximityto a bone surface, and a spanning portion 230 s that connects theproximal and distal portions.

The proximal portion 230 p of the wing 230 can include a central opening236 sized to receive at least a portion of the closure mechanism 208therethrough. For example, the central opening 236 can be sized toreceive the proximal portion 208 p of the closure mechanism 208therethrough. The central opening 236 can include a smooth, non-threadedinterior surface to allow the wing 230 and the closure mechanism 208 tobe freely rotatable with respect to one another. A proximal-facingsurface 240 of the proximal portion 230 p of the wing 230 can be domedor rounded to provide an atraumatic surface and reduce the risk oftissue irritation post-implantation. A distal-facing surface 242 of theproximal portion 230 p of the wing 230 can be configured to engage theproximal-facing surface of the receiver member 204. The distal-facingsurface 242 can form a negative or a substantial negative of theproximal-facing surface of the receiver member 204. For example, theproximal-facing surfaces of the arms 214A, 214B of the receiver member204 can be radially-convex, and the distal-facing surface 242 of thewing 230 can define a radially-concave channel that receives the convexends of the arms. In some embodiments, the central opening 236 oranother feature of the wing 230 can be sized and configured to snap ontoor capture a portion of the closure mechanism 208 or a proximal surfaceof the receiver member 204.

The distal portion 230 d of the wing 230 can include one or moreopenings 244 configured to receive a bone anchor 234 therethrough. Whiletwo bone anchor openings 244 are shown in the illustrated embodiment, itwill be appreciated that the wing 230 can include any number of boneanchor openings (e.g., one, two, three, four, five, and so on). The boneanchor openings 244 can include any of a number of features foraccepting bone anchors 234 at varying angles and/or increasing thesecurity and stability with which bone anchors can be secured to thewing 230. Exemplary features that can be included are disclosed in U.S.Pat. No. 7,637,928, issued on Dec. 29, 2009; U.S. Pat. No. 8,343,196,issued on Jan. 1, 2013; U.S. Pat. No. 8,574,268, issued on Nov. 5, 2013;U.S. Pat. No. 8,845,697, issued on Sep. 30, 2014; and U.S. Pat. No.8,758,346, issued on Jun. 24, 2014, which are each hereby incorporatedby reference herein. For example, the bone anchor openings 244 can be atleast partially threaded to receive a variable-angle locking screwhaving a threaded proximal head. As shown, the openings 244 can have aplurality of columns of threads spaced apart to define a plurality ofnon-threaded recesses. In the illustrated embodiment, each of theopenings 244 has four columns of threads. The columns of threads can bearranged around the inner surface of each of the openings 244 forengaging threads on the heads of locking auxiliary bone anchors and/orvariable-angle locking auxiliary bone anchors. The auxiliary boneanchors 234 can thus be locked with the wing 230 coaxially with thecentral axis of the opening 244 or at a selected angle within a range ofselectable angles relative to the central axis of the opening. Theauxiliary bone anchors 234 can include features to facilitate thisvariable-angle locking, such as a proximal head that is at leastpartially spherical having a thread with a profile that follows thearc-shaped radius of curvature of the spherical portion of the head. Thevariable-angle capability of the screw/opening interface can allow theuser to place locking auxiliary bone anchors into the bone at any anglewithin defined angulation limits, thus providing improved placementflexibility and eliminating or reducing the need to conform the distalportion of the wing to the bone surface to achieve a desired insertionangle. The auxiliary bone anchors 234 can be driven into the bone withdiverging or converging longitudinal axes (relative to each other and/orrelative to the primary bone anchor 202) which can provide improvedresistance to pullout. In some embodiments, the interior surfaces of theopenings 244 can be smooth or spherical, without threads or lockingfeatures.

The central axis of each of the openings 244 can be perpendicular orsubstantially perpendicular to a distal-facing surface 246 of the wing230. Alternatively, one or more of the openings can have a central axisthat extends at an oblique angle with respect to the distal-facingsurface 246. In the illustrated embodiment, the central axis of eachopening 244 extends at an angle of about 7 degrees with respect to thedistal-facing surface 246. In some embodiments, the central axis of eachopening 244 can extend at an angle of between about 0 degrees and about15 degrees with respect to the distal-facing surface 246 (e.g.,embodiments used for bony attachment locations that allow directproximal to distal screw insertion). In some embodiments, the centralaxis of each opening 244 can extend at an angle of between about 15degrees and about 45 degrees with respect to the distal-facing surface246 (e.g., embodiments used for bony attachment locations where anangled trajectory may avoid or target specific anatomy). Angled ordivergent central axes can advantageously increase the pulloutresistance of the construct.

The distal portion 230 d of the wing 230 can have a distal-facingsurface 246 configured to contact bone or to be disposed in closeproximity to bone. The distal-facing surface 246 can include teeth,texturing, or other surface features to enhance grip with the adjacentbone. The distal portion 230 d of the wing 230 can have a lateralsurface 248 that abuts a sidewall of the receiver member 204. Thelateral surface 248 can form a negative of the sidewall of the receivermember 204, such that the distal-portion 230 d of the wing 230 can hugthe receiver member with minimal or zero gap therebetween. For example,the lateral surface 248 can be concave with a radius of curvature equalor substantially equal to a radius of curvature of the exterior sidewallof the receiver member 204.

The spanning portion 230 s of the wing 230 can extend vertically in aproximal-distal direction to join the proximal portion 230 p of the wingto the distal portion 230 d of the wing. The spanning portion 230 s ofthe wing 230 can have a lateral surface 250 that engages a sidewall ofthe receiver member 204. The lateral surface 250 can form a negative ofthe sidewall of the receiver member 204, such that the spanning portion230 s of the wing 230 can hug the receiver member with minimal or zerogap therebetween. For example, the lateral surface 250 can be concavewith a radius of curvature equal or substantially equal to a radius ofcurvature of the exterior sidewall of the receiver member 204. Thelateral surface 250 can also include one or more protrusions 252 forengaging a corresponding recess 254 formed in the sidewall of thereceiver member 204, or one or more recesses in which a protrusion ofthe receiver member is received. The interaction between the one or moreprotrusions 252 and the one or more recesses 254 can be effective tolimit or prevent rotation of the wing 230 with respect to the receivermember 204. This interaction can also be effective to limit or preventmovement of the wing 230 with respect to the receiver member 204 along aproximal-distal axis. The spanning portion 230 s can include webbing orribs 256 to enhance the structural rigidity of the wing 230. The ribs256 can be formed in an outer surface of the spanning portion 230 s,opposite to the lateral surface 250 that engages the receiver member204.

The proximal portion 230 p, distal portion 230 d, and spanning portion230 s can be formed integrally as a monolithic unit as shown, or one ormore of said components can be separate and selectively attachable tothe others. In some embodiments, a kit of modular components can beprovided to allow selection of the components most appropriate for agiven use. For example, a spanning portion 230 s of appropriate heightcan be selected based on the distance between the proximal end of thereceiver member 204 and the bone surface in a given application.

One or more portions of the wing 230 can be flexible or deformable toallow the wing to be custom-tailored for a particular situation.

For example, the distal portion 230 d of the wing 230 can be flexible ordeformable to allow the distal portion to be contoured to the bonesurface. The distal portion 230 d can be contoured before implantationor in situ. The distal portion 230 d can be contoured using a separatebending instrument, or by tightening the bone anchors 234 to deform thedistal portion into intimate contact with the bone surface. The distalportion 230 d of the wing 230 can be pre-shaped or pre-contoured, e.g.,during manufacture, to match a bone surface with which the bone anchorassembly 200 is to be used.

By way of further example, the spanning portion 230 s of the wing 230can be flexible or deformable to allow the position of the bone anchoropenings 244 to be adjusted relative to the receiver member 204. Thespanning portion 230 s can be bent or flexed inwardly or outwardly(e.g., in a medial-lateral direction) to move the bone anchor openings244 inward towards the receiver member 204 or outward away from thereceiver member. Such bending can also increase or decrease theeffective height of the wing 230, to accommodate varying distances thatmay be encountered between the proximal end of the receiver member 204and the bone surface. The spanning portion 230 s can be bent or flexedup or down (e.g., in a superior-inferior direction) to move the boneanchor openings 244 relative to the receiver member 204. The spanningportion 230 s can be contoured before implantation or in situ. Thespanning portion 230 s can be contoured using a separate bendinginstrument, or by tightening the bone anchors 234 to deform the spanningportion into the desired shape. The spanning portion 230 s of the wing230 can be pre-shaped or pre-contoured, e.g., during manufacture, for agiven application.

As yet another example, the proximal portion 230 p of the wing 230 canbe flexible or deformable, and/or the connections or locations at whichthe proximal portion 230 p, the distal portion 230 d, and the spanningportion 230 s are joined can be flexible or deformable. The proximalportion 230 p, distal portion 230 d, and spanning portion 230 s can bejoined by a living hinge or other joint to allow adjustment to theirrelative positions.

The spanning portion 230 s can have an adjustable height. For example,as shown in FIGS. 2I-2M, the spanning portion 230 s can include firstand second flexible or deformable legs 258. By bending the legs 258inward towards one another, the height of the spanning portion 230 s canbe increased. By bending the legs 258 outward away from one another, theheight of the spanning portion 230 s can be decreased. Each leg 258 caninclude an upper portion and a lower portion joined by a flexible joint(e.g., a living hinge, pivot pin, or the like). Rounded or semi-circularsurfaces can be formed at the connections between the legs 258 and theproximal and distal portions 230 p, 230 d of the wing 230 to reducematerial stress as the legs are bent. Similarly, a rounded orsemi-circular cut-out can be formed where the upper portion of each leg258 meets the lower portion. The cut-out can reduce stress and alsoprovide an engagement surface for gripping the legs 258 with a toolconfigured to apply a squeezing force thereto.

The bone anchor assembly 200 can provide significant flexibility for thesurgeon. The wing 230 can be easily flipped around to be positioned oneither side of the rod 206 (e.g., on a medial side or a lateral side ofthe rod). The wing 230 can be freely rotated about the closure mechanism208 prior to final locking of the wing to the receiver member 204,allowing the auxiliary bone anchor holes 244 to be positioned at variouslocations with respect to the spinal rod 206, as shown in FIG. 2D. Asdescribed in detail above, the wing 230 can be deformable or flexible,or can include deformable or flexible portions, to allow the wing to fitsnugly with the receiver member 204, to match a contour of the bonesurface, to reposition the auxiliary bone anchor holes 244 with respectto the receiver member, and/or to adjust a height of the wing toaccommodate receiver members of different heights or situations wherethe primary bone anchor 202 is over or under inserted into the bone.

Referring again to FIG. 2A, the proximal-most extent of each auxiliarybone anchor 234 can be distal to the spinal rod 206. In otherembodiments, the proximal-most extent of each auxiliary bone anchor 234can be distal to the distal-most extent of the receiver member 204.These configurations can advantageously reduce the overall profile ofthe assembly 200. The wing 200 can be Z-shaped or substantiallyZ-shaped.

The wing 230 can extend radially outward from the receiver member 204(e.g., by a distance equal to the width of the distal portion 230 d ofthe wing). The degree to which the wing 230 extends outward from thereceiver member 204 can vary among different embodiments. In theillustrated embodiment, the ratio of wing extension to rod diameter (orthe ratio of wing extension to the width of the rod-receiving recess inthe receiver member) is about 2:1. In some embodiments, this ratio canbe less than about 10:1, less than about 5:1, less than about 3:1, lessthan about 2:1, less than about 1:1, and/or less than about 0.5:1. Insome embodiments, the ratio can be about 10:1, about 5:1, about 3:1,about 2:1, about 1:1, or about 0.5:1.

The centers of the auxiliary bone anchor holes 244 (and thus at least aportion of the auxiliary bone anchors 234 disposed therein) can bespaced radially apart from the center of the opening in the receivermember 204 in which the primary bone anchor 202 is disposed. In someembodiments, this spacing can be less than about 2.5 times the diameterof the receiver member 204. In some embodiments, this spacing can beless than about 2 times the diameter of the receiver member 204. In someembodiments, this spacing can be less than the diameter of the receivermember 204. In some embodiments, this spacing can be between about 5 mmand about 10 mm. In some embodiments, this spacing can be about 7.5 mm.In some embodiments, the auxiliary bone anchors 234 can be containedwithin an envelope no bigger than 2.5 times the diameter of the receivermember 204. In some embodiments, the auxiliary bone anchors 234 can becontained within an envelope no bigger than 2 times the diameter of thereceiver member 204.

The auxiliary bone anchors 234 can include any of the features of thebone anchor 202 described above, and any of a variety of other bonescrews or other anchors can be used instead or in addition. As notedabove, the auxiliary bone anchors 234 can have threaded proximal headsto facilitate variable-angle locking with the wing 230. In someembodiments, the auxiliary bone anchors 234 can have a length of about 6mm to about 20 mm (e.g., in embodiments used for cervical applications).In some embodiments, the auxiliary bone anchors 234 can have a length ofabout 6 mm to about 100 mm (e.g., in embodiments used for lumbar orsacral applications). The length of the auxiliary bone anchors 234 canbe selected based on various factors, including the available safe boneat any given attachment location. The auxiliary bone anchors 234 canhave a length equal to that of the primary bone anchor 202. Theauxiliary bone anchors 234 can have a length less than that of theprimary bone anchor 202. The auxiliary bone anchors 234 can have alength that is between about 60% and about 80% of the length of theprimary bone anchor 202. The auxiliary bone anchors 234 can have alength that is about 70% of the length of the primary bone anchor 202.The auxiliary bone anchors 234 can have a length of about 10 mm. Theauxiliary bone anchors 234 can have a length of about 14 mm. In someembodiments, two 10 mm auxiliary bone anchors can be used with one 14 mmprimary bone anchor. In some embodiments, one 14 mm auxiliary boneanchor can be used with one 14 mm primary bone anchor. The auxiliarybone anchors 234 can have a shank diameter equal to that of the primarybone anchor 202. The auxiliary bone anchors 234 can have a shankdiameter less than that of the primary bone anchor 202. The auxiliarybone anchors 234 can have a shank diameter that is between about 50% andabout 70% of the shank diameter of the primary bone anchor 202. Theauxiliary bone anchors 234 can have a shank diameter that is about 60%of the shank diameter of the primary bone anchor 202.

FIGS. 3A-3I illustrate an exemplary embodiment of a bone anchor assembly300, shown with a spinal rod 306. As shown, the bone anchor assembly 300can include a bone anchor 302, a receiver member 304, a closuremechanism 308, a grommet or plate 360, and one or more auxiliary boneanchors 334. In use, a saddle portion of the plate can be disposedbetween the rod 306 and the receiver member 304 to secure the plate 360to the receiver member, thereby providing the ability to augmentfixation of the bone anchor 302 with the one or more auxiliary boneanchors 334.

Except as described below or as will be readily appreciated by onehaving ordinary skill in the art, the bone anchor 302, receiver member304, and closure mechanism 308 are substantially similar to the boneanchor 102, receiver member 104, and closure mechanism 108 describedabove. A detailed description of the structure and function thereof isthus omitted here for the sake of brevity. The bone anchor assembly 300can include any one or more of the features of the bone anchor assembly100 described above.

As shown in FIGS. 3C-3F, the grommet or plate 360 can include a primaryopening 362 configured to receive at least a portion of the receivermember 304 therethrough. The plate can also include one or more openings364 configured to receive a bone anchor 334 therethrough. While a singlebone anchor opening 364 is shown in the illustrated embodiment, it willbe appreciated that the plate 360 can include any number of bone anchoropenings (e.g., one, two, three, four, five, and so on). The bone anchoropenings 364 can include any of a number of features for accepting boneanchors 334 at varying angles and/or increasing the security andstability with which bone anchors can be secured to the plate 360.Exemplary features that can be included are disclosed in U.S. Pat. No.7,637,928, issued on Dec. 29, 2009; U.S. Pat. No. 8,343,196, issued onJan. 1, 2013; U.S. Pat. No. 8,574,268, issued on Nov. 5, 2013; U.S. Pat.No. 8,845,697, issued on Sep. 30, 2014; and U.S. Pat. No. 8,758,346,issued on Jun. 24, 2014, which are each hereby incorporated by referenceherein. For example, the bone anchor opening 364 can be at leastpartially threaded to receive a variable-angle locking screw having athreaded proximal head. As shown, the opening 364 can have a pluralityof columns of threads spaced apart to define a plurality of non-threadedrecesses. In the illustrated embodiment, the opening 364 has fourcolumns of threads. The columns of threads can be arranged around theinner surface of the opening 364 for engaging threads on the heads oflocking auxiliary bone anchors and/or variable-angle locking auxiliarybone anchors. The auxiliary bone anchor 334 can thus be locked with theplate 360 coaxially with the central axis of the opening 364 or at aselected angle within a range of selectable angles relative to thecentral axis of the opening. The auxiliary bone anchor 334 can includefeatures to facilitate this variable-angle locking, such as a proximalhead that is at least partially spherical having a thread with a profilethat follows the arc-shaped radius of curvature of the spherical portionof the head. The variable-angle capability of the screw/openinginterface can allow the user to place locking auxiliary bone anchorsinto the bone at any angle within defined angulation limits, thusproviding improved placement flexibility and eliminating or reducing theneed to conform the plate to the bone surface to achieve a desiredinsertion angle. The auxiliary bone anchor 334 can be driven into thebone with a diverging or converging longitudinal axis relative to theprimary bone anchor 302 and/or relative to other auxiliary bone anchors334, which can provide improved resistance to pullout. In someembodiments, the interior surface of the opening 334 can be smooth orspherical, without threads or locking features.

The central axis of the opening 364 can be perpendicular orsubstantially perpendicular to a distal-facing surface of the plate 360.Alternatively, the opening 364 can have a central axis that extends atan oblique angle with respect to the distal-facing surface. In theillustrated embodiment, the central axis of the opening 364 extends atan angle of about 0 degrees with respect to the distal-facing surface.In some embodiments, the central axis of the opening 364 can extend atan angle of between about 0 degrees and about 15 degrees with respect tothe distal-facing surface (e.g., embodiments used for bony attachmentlocations that allow direct proximal to distal screw insertion). In someembodiments, the central axis of the opening 364 can extend at an angleof between about 15 degrees and about 45 degrees with respect to thedistal-facing surface (e.g., embodiments used for bony attachmentlocations where an angled trajectory may avoid or target specificanatomy). An angled or divergent central axis can advantageouslyincrease the pullout resistance of the construct.

The plate 360 can include a saddle portion 366 that extends across atleast a portion of the primary opening 362. The saddle portion 366 canspan entirely across the primary opening 362, or can be cantilevered asshown to project out across the opening without contacting the oppositeside of the opening. The latter configuration can advantageouslyfacilitate bending of the saddle portion 366 with respect to the rest ofthe plate 360, thereby allowing the position of the plate with respectto the receiver member 304 to be adjusted (e.g., to bend the plate downinto contact with the bone surface). The saddle portion 366 can includea distal facing surface 366 d that mimics the distal facing surface of aspinal fixation or stabilization element with which the bone anchorassembly 300 is to be used. For example, in the case of a cylindricalspinal rod 306, the distal-facing surface 366 d of the saddle portion366 can define a section of a cylinder having a radius equal to orsubstantially equal to the diameter of the spinal rod. Theproximal-facing surface 366 p of the saddle portion 366 can define aseat configured to receive the spinal fixation or stabilization elementtherein. In the illustrated embodiment, the seat 366 p is sized andshaped to receive a cylindrical spinal rod 306 therein. The radius ofcurvature of the proximal-facing seat 366 p can be equal to orsubstantially equal to that of the rod-receiving channel of the receivermember 304.

The saddle portion 366 can effectively divide the primary opening 362into first and second openings on either side of the saddle portion,each sized to receive a corresponding one of the arms 314A, 314B of thereceiver member 304. When assembled, the opposed arms 314A, 314B of thereceiver member can be inserted through the first and second openingssuch that the plate 360 surrounds the receiver member 304 and such thatthe saddle portion 366 is seated within the rod-receiving recess of thereceiver member. The spinal rod 306 can then be seated on theproximal-facing surface 366 p of the saddle portion 366, between theopposed arms 314A, 314B of the receiver member 304, and locked in placewith the closure mechanism 308 as described above, thereby also lockingthe plate 360 to the receiver member. An auxiliary bone anchor 334 canbe inserted through each of the one or more bone anchor openings 364 inthe plate to augment the fixation provided by the primary bone anchor302.

The primary opening 362 in the plate can be defined by a first sidewall368 that is generally ring-shaped and that intersects with a secondsidewall 370 that is also generally ring-shaped and that defines the oneor more auxiliary bone anchor openings 364. The height of the firstsidewall 368 can be reduced at the junction with the second sidewall 370or in areas adjacent thereto to facilitate bending of the plate 360 toreposition the auxiliary bone anchor opening 364 with respect to thereceiver member 304.

The first and second sidewalls 368, 370 can be formed integrally as amonolithic unit as shown, or one or more of said components can beseparate and selectively attachable to the other. In some embodiments, akit of modular components can be provided to allow selection of thecomponents most appropriate for a given use. For example, a firstsidewall 368 of appropriate size can be selected based on the size ofthe receiver member 304 or the size of the spinal rod 306. By way offurther example, one or more modular second sidewalls 370 can beattached to the first sidewall 368, e.g., depending on the number ofauxiliary bone anchors 334 that are to be used.

The second sidewall 370, and thus the auxiliary bone anchor opening 364defined thereby, can be positioned at any of a variety of locationsabout the perimeter of the first sidewall 368. In the illustratedembodiment, for example, the auxiliary bone anchor opening 364 ispositioned approximately at a “5 o'clock” or “lower” position withrespect to the saddle portion 366, such that the center point of theauxiliary bone anchor opening 364 is offset laterally from the saddleportion and aligned with an inferior end of the saddle portion. In otherembodiments, the auxiliary bone anchor opening 364 can be positionedapproximately at a “3 o'clock” or “middle” position with respect to thesaddle portion 366, such that the center point of the auxiliary boneanchor opening 364 is offset laterally from the saddle portion andaligned with a longitudinal midpoint of the saddle portion. In otherembodiments, the auxiliary bone anchor opening 364 can be positionedapproximately at a “1 o'clock” or “upper” position with respect to thesaddle portion 366, such that the center point of the auxiliary boneanchor opening 364 is offset laterally from the saddle portion andaligned with a superior end of the saddle portion. A kit can be providedincluding a plurality of plates 360, each including auxiliary boneanchor openings 364 positioned at different locations with respect tothe saddle portion 366, to give the user flexibility in locating theauxiliary bone anchor 334 relative to the rod 306. This can allow theuser to select a plate 360 that will position the auxiliary bone anchor334 in a good position to get bone purchase.

One or more portions of the plate 360 can be flexible or deformable toallow the plate to be custom-tailored for a particular situation. Forexample, as noted above, the portion of the plate 360 in which the boneanchor opening(s) 364 are formed can be bent or flexed to repositionsaid portion with respect to the portion of the plate in which thereceiver member 304 is disposed. The plate 360 can be contoured beforeimplantation or in situ. The plate 360 can be contoured using a separatebending instrument, or by tightening the bone anchors 334 to deform theplate into intimate contact with the bone surface. The plate 360 can bepre-shaped or pre-contoured, e.g., during manufacture, to match a bonesurface or construct with which the bone anchor assembly 300 is to beused.

In some cases, the thickness of the saddle portion 366 can cause thespinal rod 306 to be raised up within the receiver member 304 to adegree that prevents sufficient attachment of the closure mechanism 308or prevents attachment of the closure mechanism altogether. In suchcases, the bone anchor assembly 300 can include a cap 372, e.g., of thetype shown in FIG. 3H. The cap 372 can attach to the proximal end of thereceiver member 304. The cap 372 can include a threaded central openingsized to receive the closure mechanism 308. Accordingly, the cap 372 canfunctionally extend the height of the threaded portion of the receivermember 304 to accommodate both the rod 306 and the saddle portion 366between the rod-receiving channel of the receiver member 304 and theclosure mechanism 308. The illustrated cap 372 includes a generallyU-shaped channel sized to accommodate the spinal rod 306. The cap 372can be attached to the receiver member 304 in any of a variety of ways.For example, the cap 372 can include one or more projections that engagewith a corresponding one or more recesses formed in the receiver member304, or the receiver member can include one or more projections thatengage with a corresponding one or more recesses formed in the cap. Thecap 372 can snap fit onto the receiver member 304. The cap 372 can slideonto the receiver member 304 from the side with a tongue and groove ordovetail connection. The cap 372 can lock onto the receiver member 304by a quarter-turn rotation of the cap relative to the receiver member.

The bone anchor assembly 300 can provide significant flexibility for thesurgeon. The plate 360 can be easily flipped around to be positioned oneither side of the rod 306 (e.g., on a medial side or a lateral side ofthe rod). As described in detail above, the plate 360 can be deformableor flexible, or can include deformable or flexible portions, to allowthe plate to fit snugly with the receiver member 304, to match a contourof the bone surface, to reposition the auxiliary bone anchor hole(s) 364with respect to the receiver member, and/or to adjust a height of theplate to accommodate receiver members of different heights or situationswhere the primary bone anchor 302 is over or under inserted into thebone. The bone anchor assembly 300 is shown in FIG. 3I installed as partof a multi-level spinal fixation construct. As shown, the plate 360allows an auxiliary bone anchor 334 to be installed at the samevertebral level as the primary bone anchor 302 to augment the fixationof the primary bone anchor.

Referring again to FIG. 3A, the proximal-most extent of each auxiliarybone anchor 334 can be distal to the spinal rod 306. In otherembodiments, the proximal-most extent of each auxiliary bone anchor 334can be distal to the distal-most extent of the receiver member 304.These configurations can advantageously reduce the overall profile ofthe assembly 300.

The centers of the auxiliary bone anchor hole(s) 364 (and thus at leasta portion of the auxiliary bone anchor(s) 334 disposed therein) can bespaced radially apart from the center of the opening in the receivermember 304 in which the primary bone anchor 302 is disposed. In someembodiments, this spacing can be less than about 2.5 times the diameterof the receiver member 304. In some embodiments, this spacing can beless than about 2 times the diameter of the receiver member 304. In someembodiments, this spacing can be less than the diameter of the receivermember 304. In some embodiments, this spacing can be between about 5 mmand about 10 mm. In some embodiments, this spacing can be about 7.5 mm.In some embodiments, the auxiliary bone anchors 334 can be containedwithin an envelope no bigger than 2.5 times the diameter of the receivermember 304. In some embodiments, the auxiliary bone anchors 334 can becontained within an envelope no bigger than 2 times the diameter of thereceiver member 304.

The auxiliary bone anchors 334 can include any of the features of thebone anchor 302 described above, and any of a variety of other bonescrews or other anchors can be used instead or in addition. As notedabove, the auxiliary bone anchors 334 can have threaded proximal headsto facilitate variable-angle locking with the plate 360. In someembodiments, the auxiliary bone anchors 334 can have a length of about 6mm to about 20 mm (e.g., in embodiments used for cervical applications).In some embodiments, the auxiliary bone anchors 334 can have a length ofabout 6 mm to about 100 mm (e.g., in embodiments used for lumbar orsacral applications). The length of the auxiliary bone anchors 334 canbe selected based on various factors, including the available safe boneat any given attachment location. The auxiliary bone anchors 334 canhave a length equal to that of the primary bone anchor 302. Theauxiliary bone anchors 334 can have a length less than that of theprimary bone anchor 302. The auxiliary bone anchors 334 can have alength that is between about 60% and about 80% of the length of theprimary bone anchor 302. The auxiliary bone anchors 334 can have alength that is about 70% of the length of the primary bone anchor 302.The auxiliary bone anchors 334 can have a length of about 10 mm. Theauxiliary bone anchors 334 can have a length of about 14 mm. In someembodiments, two 10 mm auxiliary bone anchors can be used with one 14 mmprimary bone anchor. In some embodiments, one 14 mm auxiliary boneanchor can be used with one 14 mm primary bone anchor. The auxiliarybone anchors 334 can have a shank diameter equal to that of the primarybone anchor 302. The auxiliary bone anchors 334 can have a shankdiameter less than that of the primary bone anchor 302. The auxiliarybone anchors 334 can have a shank diameter that is between about 50% andabout 70% of the shank diameter of the primary bone anchor 302. Theauxiliary bone anchors 334 can have a shank diameter that is about 60%of the shank diameter of the primary bone anchor 302.

The saddle portion 366 can extend completely across the rod-receivingrecess of the receiver member 304. The saddle portion 366 can extendacross less than an entirety of the rod-receiving recess of the receivermember 304 (e.g., across only a portion of the rod-receiving recess).The saddle portion 366 can be omitted altogether. For example, the plate360 can include an alternative distal facing portion to bear against thereceiver member 304 and transfer the holding force of the auxiliary boneanchors 334 to the receiver member. Exemplary distal facing portions caninclude a lip, a shelf, a face, a tapered portion, and/or teeth that canmesh or engage with a portion of the receiver member 304.

FIGS. 4A-4E illustrate an exemplary embodiment of a bone anchor assembly400, shown with a spinal rod 406. As shown, the bone anchor assembly 400can include a bone anchor 402, a receiver member 404, a closuremechanism 408, a hook 474, a washer or collar 476, and a locking screw478. In use, the collar 476 and locking screw 478 can be used to attachthe hook 474 to the receiver member 404. The hook 474 can be hooked ontoor engaged with a portion of the patient anatomy or a nearby implant toaugment fixation of the bone anchor 402.

Except as described below or as will be readily appreciated by onehaving ordinary skill in the art, the bone anchor 402, receiver member404, and closure mechanism 408 are substantially similar to the boneanchor 102, receiver member 104, and closure mechanism 108 describedabove. A detailed description of the structure and function thereof isthus omitted here for the sake of brevity. The bone anchor assembly 400can include any one or more of the features of the bone anchor assembly100 described above.

The hook 474 can include a body portion 480 with a curved or loopedextension 482 projecting therefrom.

The extension 482 can be substantially U-shaped, with an inside curvedsurface 484 and an outside curved surface 486. The extension 482 can besized and configured to hook onto a portion of the patient's anatomy(e.g., a lamina, spinous process, or other bone structure of thepatient) or onto another implant or implant construct (e.g., across-connector, screw, rod, plate, intervertebral implant, or thelike). For example, the inside curved surface 484 can form a negative ora substantial negative of the anatomy or implant.

As shown in FIG. 4A, the hook 474 can be coupled to the lamina L of thepatient such that a proximal-facing surface 488 of the inside curve 484of the extension 482 abuts a distal facing surface of the lamina andsuch that a distal-facing surface 490 of the inside curve 484 of theextension 482 abuts a proximal-facing surface of the lamina.

While a single extension 482 is shown in the illustrated embodiment, itwill be appreciated that the hook 474 can include any number ofextensions (e.g., one, two, three, four, five, and so on).

One or more portions of the hook 474 can be flexible or deformable toallow the hook to be custom-tailored for a particular situation. Forexample, the extension 482 of the hook 474 can be contoured to match theanatomy or implant onto which the extension is to be hooked. The hook474 can be contoured before implantation or in situ. The hook 474 can becontoured using a separate bending instrument, or by tightening thelocking screw 478 to deform the hook into intimate contact with theanatomy or implant. The hook 474 can be pre-shaped or pre-contoured,e.g., during manufacture, to match an anatomy or implant with which thebone anchor assembly 400 is to be used.

In some embodiments, a kit of modular hooks 474 can be provided to allowselection of the hook or hooks most appropriate for a given use. Forexample, hooks 474 having extensions 482 of varying sizes thatcorrespond to the varying sizes of laminae found in a patient populationor the varying sizes of laminae found within a single human spine can beincluded in the kit and the most appropriately sized hook can beselected for the surgery. Hooks 474 of varying size and/or varyingoffset relative to the receiver member 404 can be included in a kit.

The body portion 480 of the hook 474 can include an opening 492 forreceiving the locking screw 478 to secure the hook to the collar 476.The opening 492 can be threaded such that the locking screw 478 can bethreaded into the opening. The body portion 480 of the hook 474 caninclude a lateral surface 494 that engages a sidewall of the receivermember 404. The lateral surface 494 can form a negative of the sidewallof the receiver member 404, such that the hook 474 can hug the receivermember with minimal or zero gap therebetween. For example, the lateralsurface 494 can be concave with a radius of curvature equal orsubstantially equal to a radius of curvature of the exterior sidewall ofthe receiver member 404.

The collar 476 can include a first opening 496A sized to receive atleast a portion of the receiver member 404 therethrough and a secondopening 496B sized to receive the locking screw 478 therethrough. Thefirst and second openings 496A, 496B can intersect one another, suchthat the collar 476 defines a “snowman” or “figure eight” shaped centralopening. The collar 476 can include one or more engagement features forforming a positive interlock with the receiver member 404, which canadvantageously prevent the collar from inadvertently sliding off of thereceiver member. For example, the collar 476 can include one or moreprojections 498 that extend radially inward into the first opening 496Ato engage corresponding one or more recesses 499 formed in an exteriorsidewall of the receiver member 404. In other embodiments, the recessescan be formed in the collar 476 and the projections can be formed on thereceiver member 404. The first opening 496A can include one or moreflats (e.g., opposed parallel, planar sidewalls as shown) that mate withcorresponding one or more flats (e.g., opposed parallel, planarsidewalls) of the receiver member 404 to prevent rotation of the collar476 with respect to the receiver member.

The second opening 496B of the collar 476 can be circular orsemi-circular to accommodate the cylindrical shaft of the locking screw478. In other embodiments, the second opening 496B can be elongated toallow the locking screw 478 to be secured at any of a variety oflocations along a length of the elongated opening. This canadvantageously allow the distance between the receiver member 404 andthe hook 474 to be adjusted as desired. The second opening 496B can havea conical or tapered countersink shape as shown such that, as thelocking screw 478 is tightened, the collar 476 is pushed to the right inFIG. 4A, cinching in the receiver member 404 and locking down the entireassembly.

When assembled, the collar 476 can sit above the spinal rod 406 andextend around the outer periphery of the receiver member 404 to securethe hook 474 to the side of the receiver member. The hook 474 can behooked onto patient anatomy or another implant to augment the fixationof the bone anchor assembly 400. In some embodiments, the hook 474 canbe hooked onto an anatomical structure at the same vertebral level asthe bone anchor 402 is inserted. Thus, for example, the bone anchor 402can be advanced into the pedicle or lateral mass of a vertebra and thehook 474 can be hooked onto a lamina of that same vertebra. As shown inFIG. 4A, the collar 476 does not interfere with insertion of the closuremechanism 408 into the receiver member 404, or with tightening orloosening of the closure mechanism. In addition, the hook 474 and collar476 can be attached to the receiver member 404 after the rod 406 isinstalled in the receiver member.

The bone anchor assembly 400 can provide significant flexibility for thesurgeon. The collar 476 and hook 474 can be easily flipped around to bepositioned on either side of the rod 406 (e.g., on a medial side or alateral side of the rod). The hook 474 can be deformable or flexible, orcan include deformable or flexible portions, to allow the hook to fitsnugly with the receiver member 404, to match a contour of the bonesurface, to reposition the hook with respect to the receiver member,and/or to adjust a height of the hook to accommodate receiver members ofdifferent heights or situations where the primary bone anchor 402 isover or under inserted into the bone.

As shown in FIG. 4E, instead of using a locking screw 478 and a collar476 that wraps around the receiver member 404, the hook 474 can attachto the receiver member in a manner similar to that used to attach thewing 230 of FIGS. 2A-2M. In particular, the hook can include a proximalportion 474 p that sits atop the opposed arms 414A, 414B of the receivermember 404 and that defines a central opening through which a closuremechanism 408 in the form of an extended threaded post is received. Thehook 474 can be locked onto the closure mechanism 408 and the receivermember by a threaded nut 432.

The hook 474 can be attached to the receiver member 404 after thereceiver member and the bone anchor 402 are coupled to the bone, whichcan advantageously give the surgeon more flexibility for insertion andalso allow insertion of the bone anchor and receiver member with anunobstructed view. In addition, the hook 474 can be coupled to thereceiver member 404 such that the bone anchor 402 does not restrictmovement of the hook. The hook 474 can thus be positioned with respectto the bone anchor 402 at least with as many degrees of freedom as thereceiver member 404.

An exemplary method of using the bone anchor assemblies disclosed hereinis described below.

The procedure can begin by forming an open or percutaneous incision inthe patient to access a bone in which a bone anchor assembly is to beimplanted. The bone can be prepared to receive the bone anchor assemblyas known in the art. For example, a pedicle of a vertebra can beprepared using standard awl, probe, and tap steps.

The bone anchor can then be advanced into the bone. If the user feelsthat the purchase of the bone anchor is inadequate, or that auxiliaryfixation would otherwise be desirable, an auxiliary fixation member canbe added to the bone anchor assembly.

For example, referring to the embodiment of FIGS. 2A-2M, a spinal rod206 can be seated in the receiver member 204 and a closure mechanism 208can be threaded down onto the rod. A wing 230 can then be positionedover the closure mechanism 208 and secured in place with the nut 232.One or more auxiliary bone anchors 234 can be inserted through the wing230 to attach the construct to the bone at a second location (or at morethan two locations). The method can include bending or flexing the wing230 to better fit the receiver member 204 or bone surface, for exampleby squeezing legs 258 of the wing together to increase a height of thewing.

As another example, referring to the embodiment of FIGS. 3A-3I, a plate360 can be seated in the receiver member 304 and a rod 306 can bepositioned over the plate and secured to the receiver member using aclosure mechanism 308. A cap 372 can be used if the height of the rod306 and plate 360 exceeds the design height of the receiver member 304.One or more auxiliary bone anchors 334 can be inserted through the plate360 to attach the construct to the bone at a second location (or at morethan two locations). The method can include bending or flexing the plate360 to better fit the receiver member 304 or bone surface.

As another example, referring to the embodiment of FIGS. 4A-4E, a spinalrod 406 can be seated in the receiver member 404 and a closure mechanism408 can be threaded down onto the rod. A collar 476 can then bepositioned over the receiver member 404 and secured to a hook 474 usinga locking screw 478. The hook 474 can be hooked onto a portion of thepatient's anatomy or a nearby implant to augment the fixation of thebone anchor assembly 400. The method can include bending or flexing thehook 474 to better fit the receiver member 404 or the anatomy orimplant.

The above steps can be repeated to install additional bone anchorassemblies at the same or at different vertebral levels, with or withoutauxiliary fixation members. Final tightening or other adjustment of theconstruct can be performed and the procedure can be completed usingknown techniques and the incision closed.

In any of the above embodiments or methods, the primary bone anchor canbe omitted and the user can rely solely on the one or more auxiliaryfixation features to secure the bone anchor assembly. This canadvantageously allow the position of the fixation to be completelyoffset from the receiver member, for example if an initially placed boneanchor needs to be removed due to improper positioning or inadequatepurchase, or when the receiver member needs to be positioned over alocation where a bone anchor cannot be inserted.

While the methods illustrated and described herein involve a bone anchorassembly placed in the pedicle or lateral mass of vertebral bone, itwill be appreciated that the systems and methods herein can be used inany bone, in non-bone tissue, or in non-living or non-tissue objects.

The auxiliary fixation members disclosed herein can be implanted in thesame surgical procedure as the bone anchor, receiver member, and spinalrod, or, in the case of revision surgery, during a subsequent surgicalprocedure.

It should be noted that any ordering of method steps expressed orimplied in the description above or in the accompanying drawings is notto be construed as limiting the disclosed methods to performing thesteps in that order. Rather, the various steps of each of the methodsdisclosed herein can be performed in any of a variety of sequences. Inaddition, as the described methods are merely exemplary embodiments,various other methods that include additional steps or include fewersteps are also within the scope of the present invention.

As evident from the foregoing, in at least some embodiments, the systemsand methods disclosed herein can provide enhanced fixation for a givensurgical site, providing greater bone fixation strength at a givenlocation without necessarily requiring moving the fixation to anadditional vertebra or skipping/increasing the involved vertebrallevels.

The bone anchor assemblies disclosed herein and the various componentparts thereof can be constructed from any of a variety of knownmaterials. Exemplary materials include those which are suitable for usein surgical applications, including metals such as stainless steel,titanium, or alloys thereof, polymers such as PEEK, ceramics, carbonfiber, and so forth. The various components of the devices disclosedherein can be rigid or flexible. One or more components or portions ofthe device can be formed from a radiopaque material to facilitatevisualization under fluoroscopy and other imaging techniques, or from aradiolucent material so as not to interfere with visualization of otherstructures. Exemplary radiolucent materials include carbon fiber andhigh-strength polymers.

The systems and methods disclosed herein can be used inminimally-invasive surgery and/or open surgery. While the systems andmethods disclosed herein are generally described in the context spinalsurgery, it will be appreciated that the systems and methods disclosedherein can be used with any human or animal implant, in any of a varietyof surgeries performed on humans or animals, and/or in fields unrelatedto implants or surgery.

Although specific embodiments are described above, it should beunderstood that numerous changes may be made within the spirit and scopeof the concepts described. Accordingly, it is intended that thisdisclosure not be limited to the described embodiments, but that it havethe full scope defined by the language of the following claims.

The invention claimed is:
 1. A bone anchor assembly, comprising: a boneanchor; a receiver member coupled to a proximal end of the bone anchorand defining a recess configured to receive a rod; a closure mechanismthreadably mated to the receiver member; a wing having a proximalportion with a distal surface that bears against the receiver member,the proximal portion being disposed proximal to the receiver member, adistal portion that defines a bone anchor opening, the distal portionhaving a lateral surface that is distal to a rod seat of the receivermember and a proximal surface that is distal to the distal surface ofthe proximal portion, and a spanning portion that connects the proximaland distal portions, the spanning portion having a lateral surface thatextends along a sidewall of the receiver member; and a nut configured tothreadably engage the closure mechanism to secure the proximal portionof the wing to the proximal end of the receiver member.
 2. The assemblyof claim 1, wherein the closure mechanism comprises a threaded post andwherein the wing includes an opening through which at least a portion ofthe threaded post is disposed.
 3. The assembly of claim 1, wherein thewing is rotatable about the closure mechanism.
 4. The assembly of claim1, wherein a distal-facing surface of the proximal portion of the wingbears against a proximal terminal end of the receiver member.
 5. Theassembly of claim 1, wherein the lateral surface of the distal portionof the wing forms a negative of the sidewall of the receiver member andwherein the lateral surface of the spanning portion of the wing forms anegative of the sidewall of the receiver member.
 6. The assembly ofclaim 1, wherein the lateral surface of the spanning portion of the wingincludes a protrusion that engages a corresponding recess formed in thereceiver member.
 7. The assembly of claim 1, wherein the spanningportion hugs the sidewall of the receiver member.
 8. The assembly ofclaim 1, wherein the receiver member is polyaxially movable relative tothe bone anchor.
 9. The assembly of claim 1, further comprising anauxiliary bone anchor disposed in the bone anchor opening of the distalportion of the wing.
 10. The assembly of claim 9, wherein theproximal-most extent of the auxiliary bone anchor is distal to a rodwhen the rod is disposed in the recess of the receiver member.
 11. Theassembly of claim 9, wherein the proximal-most extent of the auxiliarybone anchor is distal to the distal-most extent of the receiver member.12. The assembly of claim 1, wherein the spanning portion has anadjustable height.
 13. The assembly of claim 12, wherein the spanningportion comprises first and second legs movable toward one another toincrease the height of the spanning portion and movable away from oneanother to decrease the height of the spanning portion.
 14. The assemblyof claim 1, wherein the spanning portion is deformable to allow thedistal portion of the wing to be angled to match an abutting bonesurface.
 15. A bone anchor assembly, comprising: a bone anchor; areceiver member coupled to a proximal end of the bone anchor anddefining a recess configured to receive a rod; a closure mechanismthreadably mated to the receiver member; a wing having a proximal matingportion disposed proximal to the receiver member, the proximal portionhaving a distal surface that bears against the receiver member to matethe wing to the receiver member, a distal portion that defines aplurality of bone anchor openings, and a spanning portion that connectsthe proximal and distal portions, the distal portion having a proximalsurface that is distal to the distal surface of the proximal portion;and a nut configured to threadably engage the closure mechanism tosecure the proximal portion of the wing to the proximal end of thereceiver member.
 16. The assembly of claim 15, wherein the spanningportion includes a protrusion for engaging a sidewall of the receivermember.
 17. The assembly of claim 16, wherein the protrusion engages arecess formed in the sidewall of the receiver member.
 18. The assemblyof claim 15, wherein the spanning portion has ribs on an outer surfacethereof.
 19. The assembly of claim 15, wherein a central axis thatextends through at least one of the plurality of openings issubstantially parallel to a central axis that extends through an openingin the proximal portion.